Porosity and Defect Engineered Activated Carbon from Wood Apple Shell for Enhanced Electrochemical Capacitor

Abstract

The use of biomass-derived activated carbon (AC) can combine economic viability and environmental sustainability, thereby addressing the challenges of resource availability and environmental impact. Therefore, we have synthesized AC using wood apple shell (WAS) as the biomass and one-step chemical activation with zinc dichloride (ZnCl₂). The prepared WAS-AC powder was activated at different temperatures ranging from 600 to 800 °C. Structural analysis verified the formation of an amorphous structure and high specific surface area of 942 m² g^–1 with a pore volume of 0.2 cm³ g^–1, whereas the I_D/I_G ratio increased with the activation temperature, confirming the graphitization and defect control within the WAS-AC powder. Furthermore, the electrochemical performances of the prepared WAS-AC electrodes were examined in a neutral electrolyte (1 M Na₂SO₄); the WAS-AC700 electrode achieved the highest specific capacitance of 210 F g^–1 at a current density of 0.5 A g^–1 and a capacitive retention of 96% after 5000 cycles at a current density of 16 A g^–1. Additionally, the symmetric Swagelok cell-type electrochemical capacitor (EC) device based on WAS-AC700 electrodes and 1 M Na₂SO₄ electrolyte demonstrated a 72 F g^–1 specific capacitance at a 0.5 A g^–1 current density and energy densities of 9.93/6.67 Wh kg^–1 at power densities of 250/8000 W kg^–1. These results highlight the promising application of wood apple shell-derived activated carbon for high-performance EC.